It is fall in Pennsylvania's Lancaster County, and Jacob Stoltzfoos is working his field much the way his forebears did three centuries ago--tugging at the yoke of a Belgian draft mule. The only sounds he hears are the snap of a rein across the mule's hindquarters, the simple mechanical whirl of his corn-harvesting machine and the creak of his oak-plank wagon as he hauls another stack of feed corn to his son-in-law's silo. Like their ancestors, Jacob and his kin light their farmhouses with gas lanterns and drive carriage horses--never automobiles--back and forth to town.